Bacteriophage T7 RNA polymerase-controlled specific gene expression in Pseudomonas

The rifampicin (Rif)-resistant RNA polymerase of phage T7 has proved invaluable for the exclusive over-expression, in Escherichia coli, of genes cloned downstream from the T7 phi 10 promoter [Tabor and Richardson, Proc. Natl. Acad. Sci. USA 82 (1985) 1074-1078]. Here, we demonstrate that the system can be extended to Gram-negative bacteria other than E. coli, by the use of compatible wide host range plasmids. As an example, the Rif-resistant in vivo synthesis and specific radiolabelling of E. coli galactokinase in Pseudomonas ATCC19151, is demonstrated. The incidental observation that 30 min after treatment with Rif, two polypeptides continue to be synthesized in plasmid-free Pseudomonas ATCC19151, indicates that these proteins are produced by very stable mRNA species.